Methods of copper extraction

ABSTRACT

The hydrometallurgical copper extraction processes of the present teachings generally including two steps: a conditioning or activating step using low concentrations of ammonia and ammonium in an aqueous solution; and an acid leaching step. The processes of the present teachings can be performed at low temperature, for example, at ambient temperature, and at atmospheric pressure.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 62/009,017, filed on Jun. 6, 2014, the entirecontents of which are incorporated by reference herein.

FIELD

The present teachings relate to copper extraction and recoveryprocesses. More specifically, the present teachings relate tohydrometallurgical copper extraction processes.

BACKGROUND

Pure copper is rarely found in nature. Instead copper is usuallycombined with other elements in copper ores. Over a dozen copper oresare mined commercially around the world. Sulfide ores, in which copperis bonded to sulfur, are the most common. Other copper ores includeoxide ores, carbonate ores, and mixed ores.

The processes for extracting copper from a copper ore varies accordingto the type of ore, the desired purity level of the final product, andother factors. Each process typically includes a series of steps duringwhich unwanted components are removed physically, chemically and/orelectrochemically, with the purity of copper increasing during theprocess. The first step often is the physical concentration of a copperore into a copper concentrate, in which the level of copper can beincreased from a few percent up to about 20% to 30%.

The extraction processes can be hydrometallurgical or pyrometallurgical.Hydrometallurgical processing of copper ores often results in incompleterecovery of copper and other precious metals, long cycle times, poorproduct quality, and the difficulty in disposal and/or treatment ofreagents and by-products of the aqueous processes. Alternative copperextraction processes, particularly for refractory materials such aschalcopyrite or copper concentrates, can be conducted at hightemperatures, under high pressure (e.g., an increased partial pressureof oxygen), and/or with strong chemical oxidants or expensive reagents.

Chalcopyrite (CuFeS₂) is one of the most abundant copper-bearingminerals, which accounts for approximately 70 percent of the world'sknown copper reserves. For more than 30 years, a significant number ofprocesses have been developed to leach copper from chalcopyrite. Anumber of demonstration plant operations have been conducted, but noneof the processes have become completely commercially operational. Duringthe past decades, there has been a decline in copper grades, oftenremarked upon as a future challenge to the copper industry. The declinein ore grades is projected to continue and, in addition, ore mineralogywould become more complex. The need to process low-grade and/or complexchalcopyrite-containing ores has been the main driver for thedevelopment of hydrometallurgical processes.

Thus, there is a need to improve the hydrometallurgical extraction ofcopper from copper ores and copper concentrates.

SUMMARY

In light of the foregoing, the present teachings provide methods ofextracting and of recovering copper from a copper ore or a copperconcentrate that can address various deficiencies and/or shortcomings ofthe state-of-the-art, including those outlined above. In particular,unlike ammonia leaching processes that dissolve copper into solution,the processes of the present teachings can condition or activate acopper ore or a copper concentrate, using an aqueous solution thatincludes a concentration of ammonia and ammonium insufficient todissolve directly a significant amount of the copper content in thecopper ore or the copper concentrate. Copper can be recovered from theconditioned or activated copper ore or copper concentrate using standardacid leaching processes followed by standard copper recovery downstreamoperations such as solvent extraction and electrowinning.

More specifically, the copper extraction processes of the presentteaching can be applicable to various copper ores and minerals such aslow-grade and chalcopyrite-containing ores and generally including twosteps: a conditioning or activating step; and an acid leaching step.Processes of the present teachings can be performed at low temperature,for example, at ambient temperature or about 30° C. Processes of thepresent teachings can be performed at atmospheric pressure. In additionto these mild processing conditions, the processes of the presentteachings generally do not require expensive reagents or strong chemicaloxidants. Rather, low concentrations of relatively inexpensive andreadily available reagents can be used. For example, the processes ofthe present teachings can permit the high yield extraction and recoveryof copper from high percentage chalcopyrite-containing ores at arelatively high rate.

Thus, in one aspect, the present teachings provide methods of extractingcopper from a copper ore or a copper concentrate. The methods generallyinclude a conditioning or activating step such as contacting a copperore or a copper concentrate with an aqueous solution comprising ammoniaand ammonium in the presence of an oxygen gas-containing fluid such asair to provide a (solid) activated copper ore or a (solid) activatedcopper concentrate; and an acid leaching step such as leaching with anacid the solid activated copper ore or the solid activated copperconcentrate to provide a pregnant leaching solution. The methods caninclude recovering the copper from the pregnant leaching solution.

In various embodiments, the conditioning or activating step of themethods of the present teachings can include contacting at a temperatureless than about 50° C. a copper ore or a copper concentrate with anaqueous solution comprising ammonia and ammonium in the presence of anoxygen gas-containing fluid to provide an activated copper ore or anactivated copper concentrate, which activated copper ore or activatedcopper concentrate can be subjected to an acid leaching process.

In some embodiments, the conditioning or activating step of the methodsof the present teachings can include contacting a copper ore or a copperconcentrate with an aqueous solution comprising ammonia and ammonium inthe presence of an oxygen gas-containing fluid to provide an activatedcopper ore or an activated copper concentrate, where the aqueoussolution has a pH between about 8 to about 10. The activated copper oreor the activated copper concentrate then can be subjected to an acidleaching process.

In certain embodiments, the conditioning or activating step of themethods of the present teachings can include contacting at atmosphericpressure a copper ore or a copper concentrate with an aqueous solutioncomprising ammonia and ammonium in the presence of an oxygengas-containing fluid to provide a solid activated copper ore or a solidactivated copper concentrate, which solid activated copper ore or asolid activated copper concentrate can be subjected to an acid leachingprocess.

In various embodiments, the methods of the present teachings can includerepeating the conditioning or activating step and the acid leachingstep. For example, the methods can include collecting the solidsremaining after leaching with an acid; repeating the contacting stepwith the collected solids to provide activated solids; and leaching withan acid the activated solids to provide another pregnant leachingsolution.

In some embodiments, the methods of the present teachings can includeseparating the solid activated ore or the solid activated copperconcentrate from the aqueous solution comprising ammonia and ammonium.The separated aqueous solution comprising ammonia and ammonium then canbe reused in another contacting step with another copper ore or anothercopper concentrate, or with the collected solids remaining afterleaching an activated copper ore or concentrate with an acid. In suchmethods, the separated or recovered aqueous solution can be reusedseveral times without any substantial changes to the solution, otherthan eventual addition of reagents and/or water to replenish thesolution to its original condition.

In another aspect, the present teachings include copper recovered fromor using a process as taught and described herein as well as articles ofmanufacture made with the copper recovered from or using a process astaught and described herein.

The foregoing as well as other features and advantages of the presentteachings will be more fully understood from the following figures,description, examples, and claims.

DESCRIPTION OF DRAWING

It should be understood that the drawing described below is forillustration purposes only. The drawing is not intended to limit thescope of the present teachings in any way

FIG. 1 is a graph of the percentage of copper extracted from a highlychalcopyritic ore using an embodiment of the process of the presentteachings (triangles) compared to a standard acid leaching process(squares).

DETAILED DESCRIPTION

It now has been discovered that copper can be hydrometallurgicallyextracted from copper ores and copper concentrates, and particularlyfrom low-grade and/or complex chalcopyritic-containing ores, under mildconditions and using readily available and relatively inexpensivereagents including ammonium salts. That is, the present teachingsprovide methods or processes for the extraction and/or recovery ofcopper from copper ores and from copper concentrates using an aqueoussolution to condition or activate the copper ore or the copperconcentrate; and an acid leach of the activated copper ore or theactivated copper concentrate to create a pregnant leaching solution.

More specifically, the present teachings provide methods or processesfor the extraction and/or recovery of copper from copper ores and fromcopper concentrates using a multi-step process. In a (first)conditioning or activating step, an aqueous solution including lowconcentrations of ammonia and ammonium can contact a copper ore or acopper concentrate to provide a solid activated copper ore or a solidactivated copper concentrate. The solid activated copper ore or thesolid activated copper concentrate then can be subjected to leachingwith an acid to provide a pregnant leaching solution. Finally, themethods can include recovering the copper from the pregnant leachingsolution.

The processes of the present teachings can be applied or used in diverseoperational contexts and processes such as dump leaching, heap leaching,in situ leaching, tank leaching, vat leaching, and concentratesleaching.

Throughout the application, where compositions are described as having,including, or comprising specific components, or where processes aredescribed as having, including, or comprising specific process steps, itis contemplated that compositions of the present teachings also consistessentially of, or consist of, the recited components, and that theprocesses of the present teachings also consist essentially of, orconsist of, the recited process steps.

In the application, where an element or component is said to be includedin and/or selected from a list of recited elements or components, itshould be understood that the element or component can be any one of therecited elements or components, or the element or component can beselected from a group consisting of two or more of the recited elementsor components. Further, it should be understood that elements and/orfeatures of a composition, an apparatus, or a method described hereincan be combined in a variety of ways without departing from the spiritand scope of the present teachings, whether explicit or implicit herein.For example, where reference is made to a particular structure, thatstructure can be used in various embodiments of apparatus of the presentteachings and/or in methods of the present teachings, unless otherwiseunderstood from the context.

It should be understood that the expression “at least one of” includesindividually each of the recited objects after the expression and thevarious combinations of two or more of the recited objects unlessotherwise understood from the context and use.

The use of the term “include,” “includes,” “including,” “have,” “has,”“having,” “contain,” “contains,” or “containing,” including grammaticalequivalents thereof, should be understood generally as open-ended andnon-limiting, for example, not excluding additional unrecited elementsor steps, unless otherwise specifically stated or understood from thecontext.

The use of the singular herein, for example, “a,” “an,” and “the,”includes the plural (and vice versa) unless specifically statedotherwise.

Where the use of the term “about” is before a quantitative value, thepresent teachings also include the specific quantitative value itself,unless specifically stated otherwise. As used herein, the term “about”refers to a ±10% variation from the nominal value unless otherwiseindicated or inferred.

It should be understood that the order of steps or order for performingcertain actions is immaterial so long as the present teachings remainoperable. Moreover, two or more steps or actions may be conductedsimultaneously.

At various places in the present specification, values are disclosed ingroups or in ranges. It is specifically intended that the descriptioninclude each and every individual subcombination of the members of suchgroups and ranges and any combination of the various endpoints of suchgroups or ranges. For example, an integer in the range of 0 to 40 isspecifically intended to individually disclose 0, 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40, and aninteger in the range of 1 to 20 is specifically intended to individuallydisclose 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, and 20.

The use of any and all examples, or exemplary language herein, forexample, “such as” or “including,” is intended merely to illustratebetter the present teachings and does not pose a limitation on the scopeof the invention unless claimed. No language in the specification shouldbe construed as indicating any non-claimed element as essential to thepractice of the present teachings.

As used herein, an “ore” refers to a type of rock that contains mineralswith elements including metals that can be economically extracted fromthe rock.

A “copper ore” refers to an ore that includes a copper compoundincluding pure copper. Examples of copper ores include sulfide ores(which contain a copper sulfide), oxide ores (which contain a copperoxide), carbonate ores (which contain copper carbonate), and mixed ores.

As used herein, a “copper concentrate” refers to a copper ore that hasbeen crushed, milled and concentrated to provide an increased amount orpercentage of copper in the resulting material than found in theoriginal ore(s).

As used herein, a “copper compound” refers to the various minerals thatinclude copper as an element and can refer copper as a pure metal,unless the context dictates otherwise. Examples of minerals includingcopper are atacamite, azurite, bornite, chalcocite, chalcopyrite,chrysolcolla, covellite, cuprite, malachite, tennantite, andtetrahedrite.

As used herein, a “copper carbonate” refers to one or more members of afamily of chemical compounds and minerals where the compound or mineralcontains the element copper associated with a carbonate group. Examplesof copper carbonates include malachite (Cu(OH)₂.CuCO₃), a green powder;and azurite (Cu(OH)₂.2CuCO₃), a blue powder.

As used herein, a “copper sulfide” refers to one or more members of afamily of chemical compounds and minerals with the formula Cu_(x)S_(y),including mixed copper-metal sulfides and mixed copper-metalloidsulfides containing copper and sulfur such as mixed copper-iron sulfidesand mixed copper-arsenic sulfides. Examples of copper sulfide mineralsinclude chalcocite (Cu₂S) and covellite (CuS) and the minerals, bornite(2Cu₂S.CuS.FeS) and chalcopyrite (CuFeS₂), which are mixed copper-ironsulfides, and enargite (Cu₃AsS₄), which is a mixed copper-arsenicsulfide.

As used herein, a “copper oxide” refers to one or more members of familyof chemical compounds and minerals where the compound or mineralcontains the element copper associated with oxygen. Examples of copperoxides include cuprite (Cu₂O (cuprous oxide)), a red powder; cupricoxide (CuO), a black powder; and copper (III) oxide (Cu₂O₃).

As used herein, an “oxygen gas-containing fluid” refers to liquid and/orgas including oxygen gas or dissolved oxygen. An oxygen gas-containingfluid can be an oxygen-containing gas such as air or gaseous oxygen,both of which can be with another carrier gas or liquid. An oxygengas-containing fluid can be an oxygenated liquid such as oxygenatedwater or water including dissolved oxygen. The source of dissolvedoxygen can be the surrounding air, which can be at atmospheric pressure.

As described herein, copper extraction processes of the presentteachings generally include two steps: a first conditioning oractivating step; and a second acid leaching step. The conditioning oractivating of a copper ore or copper concentrate can provide a solidactivated copper ore or a solid activated copper concentrate, whichactivated solids can be leached with acid to provide a pregnant leachingsolution. Copper then can be recovered from the pregnant leachingsolution.

More specifically, the conditioning or activating step can includecontacting a copper ore or a copper concentrate with an aqueous solutioncomprising ammonia and ammonium in the presence of an oxygengas-containing fluid to provide a (solid) activated copper ore or a(solid) activated copper concentrate.

Unlike ammonia leaching processes, the conditioning of the copper ore orthe copper concentrate includes using an aqueous solution that includesa concentration of ammonia and ammonium insufficient to dissolvedirectly more than a majority of the copper and/or copper compounds inthe copper ore or the copper concentrate. For example, the aqueoussolution can include a concentration of ammonia and ammoniuminsufficient to dissolve directly more than about 40% of the copperrecovered from the copper ore or the copper concentrate. In certainembodiments, the aqueous solution can include a concentration of ammoniaand ammonium insufficient to dissolve directly more than about 30%, morethan about 25%, more than about 20%, more than about 15%, more thanabout 10%, more than about 8%, more than about 5%, more than about 3%,more than about 2%, or less of the copper recovered from the copper oreor the copper concentrate. In certain embodiments, the aqueous solutionincludes a concentration of ammonia and ammonium insufficient todissolve directly more than 25%, more than 20%, or more than 15% of thecopper recovered from the copper ore or the copper concentrate.

Because copper is not soluble at a pH higher than about 5, thedissolution of copper at higher pH's such as between a pH of 6 to 10 canbe accomplished by the formation of complexes, for example, withammonia. Any copper dissolved in an aqueous solution containing ammoniaand ammonium at a pH of 9 would be complexed with ammonia. The use ofthe term “directly” in relation to dissolution of copper refers to theconditions present during the step of the process or method in whichthis term is used. For example, if the aqueous solution includingammonia and ammonium can dissolve directly no more than 20% of thecopper recovered in the process, then the aqueous solution can dissolveno more than 20% of the recovered copper in the step in which theaqueous solution is being used, for example, in a conditioning oractivating step, and does not include the dissolution of copper duringother steps, for example, an acid leaching or other subsequentprocessing or steps.

In some embodiments of the methods of the present teachings, the aqueoussolution can include between about 1 mg/L to about 40 g/L of ammonia andammonium. In certain embodiments, the aqueous solution can includebetween about 1 mg/L to about 30 g/L, between about 1 mg/L to about 20g/L, between about 1 mg/L to about 15 g/L, between about 1 mg/IL toabout 10 g/L, between about 1 mg/L to about 5 g/L, between about 1 mg/Lto about 1 g/L, or between about 1 mg/L to about 500 mg/L, of ammoniaand ammonium. In particular embodiments, the aqueous solution caninclude between about 1 mg/L to about 30 g/L, between about 1 mg/L toabout 20 g/L, or about 100 mg/L to about 20 g/L.

In various embodiments of the methods of the present teachings, theammonium can be derived from one or more sources of ammonium ions, suchas ammonium carbonate, ammonium chloride, ammonium hydroxide, ammoniumnitrate, and ammonium sulfate. As used herein “ammonium” refers NH₄ ⁺ oran ammonium ion, which terms and formula can be used interchangeablyherein. In particular embodiments, the source of ammonium is ammoniumsulfate. The source of ammonia, indirectly, can be ammonium sulfate.

It should be understood that the ammonia present in the aqueous solutioncan be derived from the source of ammonium. That is, free ammonia orgaseous ammonia need not be introduced into the aqueous solution used inthe conditioning or activating step, but rather the ammonia can bederived in situ from the equilibrium of the ammonium ions in the aqueoussolution. As discussed in more detail herein, when ammonium ions are inan aqueous solution, an equilibrium exists with the ammonium ions andammonia, which equilibrium is pH dependent. Thus, upon the dissolutionof the source of ammonium in water to provide, in part, the aqueousconditioning or activating solution, ammonia can be generated, whichammonia can participate in the hydrometallurgical processes.

In some embodiments, the ammonia and ammonium can be derived fromgaseous ammonia delivered in an appropriate amount to water or anaqueous solution, whereby the ammonia in water forms an equilibriumbetween the ammonia and ammonium as described herein, which equilibriumis pH dependent.

In some embodiments of the present teachings, the conditioning oractivating step can be conducted or carried out at an atmosphericpressure. In certain embodiments, the conditioning or activating stepcan be conducted at a higher pressure, for example, in a pressurechamber or vessel such as an autoclave. The higher or increased pressurecan include an increased pressure of oxygen (e.g., an increased oxygenpartial pressure). For example, the conditioning step can be carried outor conducted at or under an increased partial pressure of oxygen orincreased oxygen partial pressure, for example, at about 5 psi, at about10 psi, at about 15 psi, or higher of oxygen partial pressure.

The aqueous solution including ammonia and ammonium can have a pH fromabout 5 to about 10. In certain embodiments, the pH of the aqueoussolution can be between about 5 to about 10, between about 6 to about10, between about 6 to about 9, between about 6 to about 8, betweenabout 7 to about 10, between about 7 to about 9, between about 7 toabout 8, between about 8 to about 10, between about 8 to about 9.5,between about 8 to about 9, between about 8.5 to about 10, between about8.5 to about 9.5, between about 8.5 to about 9, between about 9 to about10, between about 9 to about 9.5, between about 6 to about 10, orbetween about 6 to about 10. In particular embodiments, the pH of theaqueous solution can be between about 8 to about 9.5, between about 8.5to about 9.5, between about 9 to about 9.5, between about 8 to about 9,between about 8 to about 8.5, or between about 8.5 to about 9.

The pH of the aqueous solution can be adjusted, regulated and/ormaintained as appropriate for the particular conditioning or activatingprocess and other factors such as the copper ore or copper concentrateto be processed. A base such as sodium hydroxide or another alkalinecompound can be used to adjust the pH of the aqueous solution. Use of abase or alkaline compound can be avoided if the ammonia andammonium-generating reagent(s) is of sufficient alkalinity therebyproviding a pH of the aqueous solution in a range as described hereinfor the conditioning or activating step.

In some embodiments, the conditioning or activating step can beconducted or carried out at ambient temperature. The conditioning oractivating step can be conducted at a higher temperature, for example,at a temperature up to about 90° C. or about 95° C. In some embodiments,the conditioning or activating step can be conducted at a temperaturebetween about ambient temperature and about 80° C., about 75° C., about70° C., about 65° C., about 60° C., about 55° C., about 50° C., about45° C., about 40° C., or between ambient temperature and about 35° C. Incertain embodiments, the conditioning or activating step can beconducted at a temperature below about 80° C., below about 75° C., belowabout 70° C., below about 65° C., below about 60° C., below about 55°C., below about 50° C., below about 45° C., below about 40° C., or belowabout 35° C. It is also within the scope of the present teachings toconduct the conditioning or activating step at a temperature belowambient temperature. In particular embodiments, the conditioning oractivating step is conducted at ambient temperature, at a temperaturebetween ambient temperature and about 90° C., or at a temperature belowabout 50° C.

The conditioning or activating step can be conducted or carried out inthe presence of an oxygen gas-containing fluid such as anoxygen-containing gas, for example, air. The oxygen gas-containing fluidsuch as air can be considered a mild oxidant. The conditioning step istypically carried out at atmospheric pressure. Accordingly, air can bedelivered to the aqueous solution, for example, under the surface of theaqueous solution such that the oxygen gas-containing gas is bubbled intoand up through the aqueous solution to provide (dissolved) oxygen forthis processing step. Other means for providing dissolved oxygen oroxygen gas into the aqueous solution can be used. The aeration techniquecan depend on the particular process and equipment being used for theconditioning or activating step (e.g., a heap or vat or reactorconditioning or activating technique or process). Accordingly, anappropriate aeration system can be used. For example, blowers can beused to provide the necessary air or oxygen into the aqueous solution.In some embodiments, the oxygen gas-containing fluid can be oxygenatedwater (i.e., water containing dissolved oxygen) that can be deliveredinto and/or circulated through the aqueous solution. The aqueoussolution typically is aerated continuously throughout the conditioningor activating step.

It should be understood that the various parameters or conditions of theconditioning or activating step, for example, temperature, pressure, pHof the aqueous solution including ammonia and ammonium, and theconcentration of ammonia and ammonium can be varied as described hereinin various combinations and values or ranges and such combinations ofconditions and values or ranges thereof are within the scope of thepresent teachings.

Following the conditioning or activating of the copper ore or the copperconcentrate, the solid activated ore or the solid activated copperconcentrate is subjected to conventional acid leaching to create orprovide a pregnant leaching solution. As already stated, the processesof the present teachings are dissimilar from ammonia leaching processesas the conditioning or activating step does not intend to solubilize thecopper or copper compounds present in the copper ore or copperconcentrate upon treatment with the aqueous solution including ammoniaand ammonium. Rather the solid material resulting from the conditioningor activating step, i.e., the activated copper ore or activated copperconcentrate (or activated solids), is subjected to acid leaching toremove the copper and copper compounds from the solid activated ore orsolid activated copper concentrate.

The acid leaching step can be carried out at a pH of between about 1.5to about 5, for example, a pH between about 3 to about 5 or betweenabout 2 to about 4. The acid leaching step can result in the dissolutionof the copper and/or copper compounds that remained solid after theconditioning or activating step. The acid leaching step can be conductedor carried out in the presence of an oxygen gas-containing fluid, suchas air or dissolved oxygen. The acid leaching solution can be aerated asappropriate for the particular equipment and techniques used.

The acid leaching step can result in a pregnant leaching solution, forexample, a copper-loaded pregnant leaching solution. The pregnantleaching solution can have similar characteristics to pregnant leachingsolutions from standard leaching processes. The pregnant leachingsolution can have very low or trace amounts of ammonia and ammonium,which compounds can interfere with downstream solvent extractionprocesses or operations. Consequently, the pregnant leaching solutioncan be channeled through standard copper recovery downstream operationssuch as solvent extraction and electrowinning without furthermodification. In addition, the short cycle time of the acid leachingprocess can prevent the substantial dissolution of undesired chemicalspecies, for example, iron and/or chloride. Finally, the copper then canbe collected and used in standard fashion.

The acid leaching step typically is conducted on activated solids suchas the activated copper ore or the activated copper concentrate, whichactivated solids can be separated from the aqueous solution includingammonia and ammonium, i.e., the acid leaching is carried out separatefrom the conditioning or activating step and solution. However, thepresent teachings also include the direct addition of an acid (leachingacid) into the mixture resulting from the conditioning or activatingstep, thereby lowering the pH of the aqueous solution in situ.

In various embodiments, the conditioning or activating and acid leachingsteps or processes can be repeated or iterated one, two, three, or moretimes, for example, until the desired level of copper extraction isachieved. Accordingly, in some embodiments, the methods of the presentteachings can further include collecting the solids remaining afterleaching with an acid; repeating the contacting step with the collectedsolids to provide activated solids; and leaching with an acid theactivated solids to provide another pregnant leaching solution. Thisgeneral cycle can be repeated one, two, three, four, or more times asneeded or desired.

In some embodiments, where the activate copper ore or the activatedcopper concentrate is separated from the aqueous ammonia and ammoniumsolution before being subjected to acid leaching, the aqueous solutioncan be used again to condition or activate another copper ore or copperconcentrate, or the solids remaining after the acid leaching step, wherethe solids from the acid leaching step are collected and contacted withthe aqueous solution first used to condition or activate the copper oreor copper concentrate. Thus, in certain embodiments of the presentteachings, the methods can include separating the solid activated copperore or the solid activated copper concentrate from the aqueous solutioncomprising ammonia and ammonium, wherein the aqueous solution comprisingammonia and ammonium is reusable or reused in the contacting step withanother copper ore or another copper concentrate, or with the collectedsolids remaining after leaching with an acid.

In the case where the aqueous solution containing ammonia and ammoniumis separated from the activated solids and reused, the reused aqueoussolution already should be “saturated” with a small fraction of thesoluble copper complexes or copper compounds that are formed such that areused aqueous solution should not dissolve any more copper or coppercompounds present in a few or fresh copper ore or copper concentrate, orcollected solids remaining from an acid leaching step, that is contactedwith the reused aqueous solution.

Similar to reusing the aqueous solution containing ammonia and ammonium,an acid leaching solution also can be reused in the form of a raffinate.For example, after the acid leaching solution contacts an activatedcopper ore or copper concentrate to provide a pregnant leachingsolution, the copper can be depleted and recovered from the pregnantleaching solution along with the removal of other unwanted materialswhereby the resultant solution (or raffinate) can similar to theoriginal acid leaching solution, which can be reused or recirculated foradditional leaching.

The conditioning or activating step or process usually is conducted orcarried out over a time of about 6 hours to about a month, 6 weeks, 2months, or more. The initial conditioning or activating step on new orunextracted copper ore or copper concentrate typically is conducted orcarried out over a time of about 12 hours to about 3 days, to about 4days, to about 5 days, to about 6 days, to about 7 days, to about 8days, to about 9 days, to about 10 days, to about 11 days, to about 12days, to about 2 weeks, to about 3 weeks, to about a month, to about 5weeks, to about 6 weeks, or more. The acid leaching step or processusually is conducted or carried out over a time of about 30 minutes toabout several hours, for example, from about one hour to about 6 hours,12 hours, or one day, or more. Depending on the particular acid leachingprocess and equipment, cycle times can be much longer. For example, forheap leaching, a typical cycle time for acid leaching of sulfides can beup to one year, or more.

In the embodiments where the conditioning or activating and acidleaching steps are repeated, the repetition of the conditioning oractivating steps can be conducted for a shorter time such as from about3 hours to about 24 hours, for example, from about 4 hours to about 18hours, or from about 6 hours to about 16 hours, or for about 12 hours.In such cases, the acid leaching step tends to be shorter than itsinitial time. That is, the repetition of the acid leaching step canoccur over a time of about 30 minutes to about 3 hours, or about 1 hourto about 2 hours, or about 1 hour. It should be understood that thesetimes should not be considered limiting because the cycle times can varyand be longer than those mentioned above depending on the particularprocess and equipment.

Accordingly, the entire processing time to achieve the desiredextraction level of copper can be between about 1 day to about 6 toabout 7 weeks; however, between about 1 day to about 6 or 8 days is morecommon. Again, depending on the particular processes and equipment, theentire processing time can be much longer, for example, up to a month, afew months, several months, a year, a few years, or more.

In various embodiments, the present teachings provide methods ofextracting copper that include contacting a copper ore or a copperconcentrate with an aqueous solution including ammonia and ammonium inthe presence of air to provide a solid activated copper ore or a solidactivated copper concentrate; and leaching with an acid the solidactivated copper ore or the solid activated copper concentrate toprovide a pregnant leaching solution, where the aqueous solution has apH in the range of about 7 to about 10. In certain embodiments, theaqueous solution has a pH between about 8 to about 10. In particularembodiments, the aqueous solution has a pH between about 8 to about 9.5.The methods can include repeating the contacting and leaching steps withthe solids recovered from the acid leaching and/or recovering copperfrom the pregnant leaching solution.

In some embodiments, the present teachings provide methods of extractingcopper that include contacting at atmospheric pressure a copper ore or acopper concentrate with an aqueous solution including ammonia andammonium in the presence of air to provide an activated copper ore or anactivated copper concentrate; and leaching with an acid the activatedcopper ore or the activated copper concentrate to provide a pregnantleaching solution, where the aqueous solution has a pH in the range ofabout 8 to about 10. The methods can include repeating the contactingand leaching steps with the solids recovered from the acid leachingand/or recovering copper from the pregnant leaching solution.

In certain embodiments, the present teachings provide methods ofextracting copper that include contacting at atmospheric pressure in atemperature range between ambient temperature and about 90° C. a copperore or a copper concentrate with an aqueous solution including ammoniaand ammonium in the presence of air to provide an activated copper oreor an activated copper concentrate; and leaching with an acid theactivated copper ore or the activated copper concentrate to provide apregnant leaching solution, where the aqueous solution has a pH in therange of about 8 to about 10. The methods can include repeating thecontacting and leaching steps with the solids recovered from the acidleaching and/or recovering copper from the pregnant leaching solution.

In particular embodiments, the present teachings provide methods ofextracting copper that include contacting at atmospheric pressure at atemperature less than about 50° C. a copper ore or a copper concentratewith an aqueous solution including ammonia and ammonium in the presenceof air to provide an activated copper ore or an activated copperconcentrate; and leaching with an acid the activated copper ore or theactivated copper concentrate to provide a pregnant leaching solution,where the aqueous solution has a pH in the range of about 8 to about 10.The methods can include repeating the contacting and leaching steps withthe solids recovered from the acid leaching and/or recovering copperfrom the pregnant leaching solution.

As described herein, the present teachings include a copper extractionprocess that can be generally carried out in two steps. Step 1, aconditioning step, can include conditioning a copper ore or a copperconcentrate with ammonium and ammonia at low concentrations, which areinsufficient to allow the formation of substantial amounts of solublecopper ammoniacal complexes, carried out at neutral or slightly alkalinepH (e.g., a pH range from about 6 to about 10, such as a pH between 8and 9.5). The conditioning solution can include an ammonium compound ina concentration range of from about 1 mg/L to about 20 g/L or up toabout 150 g/L. The source of ammonium can include ammonium sulfate,ammonium chloride, ammonium nitrate, ammonium hydroxide, andcombinations thereof. Sodium hydroxide (or another alkaline compound)can be used to adjust the pH. The amount used can depend on theconsumption of hydroxide by the treated mineral.

Without wishing to be bound to any particular theory, in the firstconditioning or activating step, it is believed that the copper in theform of a primary sulfide (e.g., chalcopyrite), is extracted by theammoniacal solution, but due to the low concentration of ammonia(insufficient substantially to form soluble copper complexes), thecopper is not in a soluble state in the pregnant leaching solution(“PLS”), but instead in a solid state in the form of compounds that areinsoluble in almost-neutral or alkaline pH solutions, such as copperhydroxides, copper oxides, and possibly other compounds.

The hydroxides, oxides or other solid copper compounds generated,although insoluble at almost-neutral or alkaline pH, are extremelysoluble at acidic pH (e.g., below pH 4). For this reason, after thefirst step is completed, the copper can be recovered in a soluble formby relatively conventional acid leaching, which is step 2 of theextraction process.

Step 2, a conventional or standard acid leaching step, can be carriedout at a pH of about 0.5 to about 5, which can solubilize the copperthat was conditioned or activated in the first step, which copper isbelieved to be in the form of hydroxide, an oxide, or another solidcopper compound that is very soluble in acid. The acid leaching step canbe characterized by very rapid kinetics (with a cycle time significantlylower (or faster) than step 1). The result obtained is a PLS with a highconcentration of copper, very similar to the PLS from conventional acidleaching processes, and with very low amounts or traces of ammonium andammonia, which could interfere with the downstream operation of solventextraction and electrowinning (“SX-EW”).

Without wishing to be bound by any particular theory, the followingdiscussion is intended to illustrate a possible mechanism explaining thephenomena of the present teachings, without attempting to describe theonly chemical reactions involved.

During step 1 of the process of the present teachings, the copperpresent as a copper sulfide can be extracted in the form of insolublecopper hydroxide, for example, according to the following proposedequation:

CuFeS₂+4NaOH+NH₃(aq)+4O₂→Cu(OH)₂(s)+Fe(OH)₂(s)+2Na₂SO₄(aq)+NH₃(aq)

The reaction is catalyzed by the limiting aqueous ammonia, which isneither consumed nor generated in the context of the reaction.Obviously, ammonia is a gas, so that, despite being highly soluble inwater, it evaporates, which constitutes a potential source of reagentloss. However, when conducted in a closed environment process or aclosed environment such as in a reactor, the ammonia can be recovered.

In the aqueous conditioning solution, ammonia (NH₃) and ammonium (NH₄ ⁺)are in equilibrium, according to the following equilibrium equation:

NH₄ ⁺+OH⁺

NH₃(aq)

This equilibrium is, in turn, strongly influenced by pH. Thus, at a pHslightly above 9, the ratio of ammonium/ammonia is about 50:50; and atpH slightly above 8, the ratio changes to 90:10 (with very littleammonia and, thus, a very low evaporation rate, especially consideringthe low total concentration of ammonium salts used in the process).

During step 2 of the process of the present teachings, the copperhydroxide generated in step 1 is dissolved in an acid medium, accordingto the following equation (with net consumption of acid (protons)):

Cu(OH)₂(s)+H₂SO₄(aq)→Cu²⁺+SO₄ ²⁺+2H₂O

The following examples are provided to illustrate further and tofacilitate the understanding of the present teachings and are not in anyway intended to limit the invention.

Example 1 Copper Extraction from Highly Chalcopyritic Ore

The copper ore was a low copper grade, highly chalcopyritic ore,characterized by a total copper content of 0.41%, being 88% of thecopper present in the form of chalcopyrite. The granulometry of thecopper ore was brought to 100%—150 Tyler Mesh.

In a one liter Erlenmeyer flask, 120 g of the copper ore was mixed with400 mL of an ammonium sulfate solution containing 10 g/L ammoniumsulfate at a pH of 9.4. The pH of the ammonium sulfate solution wasadjusted to 9.4 by addition of sodium hydroxide. The mixture was reactedat 30° C. with mild agitation on an orbital shaker incubator for 2 days(step 1).

At the end of the reaction period, sulfuric acid was added to themixture to adjust the pH to 2.5 and standard acid leaching was performed(step 2). The acidified slurry was maintained under the same conditionsdescribed above for 2 additional hours, after which the resultingpregnant leaching solution was separated from the solid residue byfiltration. A sample of the resulting pregnant leaching solution wasanalyzed for copper content

The above process was repeated where the conditioning or activatingstep, i.e., step 1, was conducted for 4 days, 6 days, 8 days, 10 days,and 12 days, respectively. The results of the copper extraction areshown in Table 1 below and in FIG. 1.

Also shown in Table 1 and in FIG. 1 are the results of copper extractionobtained by running a parallel set of standard acid leaching using asulfuric acid solution at a pH range between 1.8 and 2.2, where thestandard acid leaching was conducted for 2 days, 4 days, 6 days, 8 days,10 days, and 12 days, respectively.

TABLE 1 Time % Copper extracted % Copper extracted (days) (conditioningand acid leaching) (acid leaching only) 0 0 0 2 42 21 4 46 23 6 55 27 858 25 10 64 28 12 68 31

In addition, prior to step 2, i.e., the addition of the sulfuric acid tothe conditioning solution, a sample of the aqueous solution containingammonium sulfate (separated from the activated and other solids bycentrifugation) was analyzed for copper content. The copper dissolved inthe aqueous solution containing ammonium sulfate after the conditioningstep was less than 5% of the copper recovered from the copper ore orcopper concentrate. Thus, the majority of the copper was dissolvedduring the standard acid leaching step rather than during theconditioning or activating step.

It should be understood that the immediately above percentage is basedon the amount of copper recovered from the process, which is distinctfrom the percentage of copper extracted from the copper ore or copperconcentrate as determined in Table 1. That is, a percentage of copperextracted is based on the total copper content of the copper ore, copperconcentrate or treated copper sample from which the copper is extracted.The percentage of copper extracted is an indicator of the performance ofthe process (i.e., the more copper extracted of the total copperavailable, the better). A percentage based on copper recovered from acopper ore or a copper concentrate such as during one iteration of theprocess (e.g., the two step process of the present teachings or a onestep ammonia leaching process) can provide a indication of the amount ofcopper present, for example, in a solution or a step of the process.

The present teachings encompass embodiments in other specific formswithout departing from the spirit or essential characteristics thereof.The foregoing embodiments are therefore to be considered in all respectsillustrative rather than limiting on the present teachings describedherein. Scope of the present invention is thus indicated by the appendedclaims rather than by the foregoing description, and all changes thatcome within the meaning and range of equivalency of the claims areintended to be embraced therein.

What is claimed is:
 1. A method of extracting copper from a copper oreor a copper concentrate, the method comprising: contacting a copper oreor a copper concentrate with an aqueous solution comprising ammonia andammonium in the presence of an oxygen gas-containing fluid to provide asolid activated copper ore or a solid activated copper concentrate,wherein the aqueous solution has a pH between about 8 to 9.5; andleaching the solid activated copper ore or the solid activated copperconcentrate with an acid to provide a pregnant leaching solution.
 2. Themethod of claim 1, further comprising recovering copper from thepregnant leaching solution.
 3. (canceled)
 4. The method of claim 1,wherein the ammonium is derived from one or more of ammonium carbonate,ammonium chloride, ammonium hydroxide, ammonium nitrate, and ammoniumsulfate.
 5. The method of claim 1, wherein the ammonia is derived insitu from the ammonium.
 6. The method of claim 1, wherein the contactingstep is carried out at atmospheric pressure.
 7. The method of claim 1,wherein the contacting step is carried out at a temperature ranging fromambient temperature to about 90° C.
 8. The method of claim 1, whereinthe oxygen gas-containing fluid comprises air.
 9. (canceled)
 10. Themethod of claim 1, wherein the copper ore or cooper concentratecomprises chalcopyrite. 11.-20. (canceled)